Management server, base station, communication system, and communication method

ABSTRACT

There is provided a management server including a holding unit for holding a location/frequency list in which location information and frequency information are associated, a list creation unit for creating an available frequency list by extracting, from the location/frequency list, frequency information corresponding to location information received from a base station, and a list transmission unit for transmitting the available frequency list created by the list creation unit to the base station.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation of and claims the benefit under 35 U.S.C. §120 ofU.S. patent application Ser. No. 13/048,988, titled “MANAGEMENT SERVER,BASE STATION, COMMUNICATION SYSTEM, AND COMMUNICATION METHOD,” filed onMar. 16, 2011, which claims the benefit under 35 U.S.C. §119 of JapanesePatent Application 2010-070266, filed on Mar. 25, 2010, each of which ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a management server, a base station, acommunication system, and a communication method.

2. Description of the Related Art

A 3G mobile telephone service called the third generation was started inJapan in 2002. In the beginning, the main application was transmissionof small packets such as sound and emails, but with the introduction ofHigh Speed Downlink Packet Access (HSDPA) and the like, download oflarger packets, such as download of music files or shared videos, hascome to be performed.

As such, with the increase in the size of packets to be downloaded,wireless communications between a base station and a terminal wereexpanded, and HSPA+ service realizing maximum 1 Mbps was started.Furthermore, LTE that uses OFDMA in downlink is expected to start around2010 and a 4G service is expected to start around 2015, and a worldwhere maximum 1 Gbps is realized with a semi-fixed terminal and maximum100 Mbps is realized in a mobile environment is becoming a reality.

To realize a wireless environment with a high communication rate asdescribed above, it is assumed that cells will shift to microcells andpicocells. Wireless environment of dead spots at the edge of a cell canbe improved to a certain degree by placing relay stations, for example,but in the case resources of base stations are in short supply, theeffect obtained by placing relay stations may be reduced.

Accordingly, in indoors having Fiber To The Home (FTTH), a high-speeddata communication environment is anticipated to be realized withoutplacing load on outdoor wireless resources, by placing small basestations called femtocell base stations.

Also, with respect to a white space which is an unused frequency band ata position or a region, it is becoming possible to use a frequency bandin the white space without license if such frequency band can be decidedto be not used. Therefore, it is expected that a technology for using alocally unused frequency band fairly and effectively will becomeimportant in the future.

Furthermore, a “special home zone” allowing frequency bands assigned tocommunications company to be freely used under the condition that nointerference is caused to a public macrocell may possibly be permittedin the future. In such a case, the current configuration of femtocellbase stations assuming operation in the frequency band assigned to eachcommunications company may not be effective.

Thus, consideration is beginning to be given to a configuration of abase station that sets a frequency band in an autonomous, decentralizedmanner. For example, a configuration of storing frequency bandinformation to be monitored in a base station, detecting receiving powerof each frequency band, deciding that the use of a frequency band whosereceiving power is at a threshold or less does not cause interference toa public macrocell, and using this frequency band as a carrier frequencyis conceivable. Also, JP-A-2004-260371 discloses, as a centralizedcontrol structure, a repeater that sets a carrier frequency based on afrequency band which has been notified.

SUMMARY OF THE INVENTION

However, in the configuration above where a carrier frequency is setbased on the receiving power at a base station, there is an underlyingissue that, if measurement means of the receiving power is broken down,for example, a frequency band that causes interference to a publicmacrocell is erroneously used for the carrier frequency. Also, in theconfiguration above where a carrier frequency is set by centralizedcontrol, since a central control station assigns a frequency bandwithout using location information of a target station (repeater), acase where communication by this target station becomes the cause ofinterference is conceivable.

In light of the foregoing, it is desirable to provide a managementserver, a base station, a communication system, and a communicationmethod which are novel and improved, and which are capable of preventinga case where communication by a base station becomes a cause ofinterference, by appropriately assigning a frequency according to thelocation of the base station.

According to an embodiment of the present invention, there is provided amanagement server which includes a holding unit for holding alocation/frequency list in which location information and frequencyinformation are associated, a list creation unit for creating anavailable frequency list by extracting, from the location/frequencylist, frequency information corresponding to location informationreceived from a base station, and a list transmission unit fortransmitting the available frequency list created by the list creationunit to the base station.

The management server may further include a list comparison unit forcomparing the available frequency list transmitted to the base stationand an available frequency list returned from the base station.

The list creation unit may create the available frequency list for eachof a plurality of base stations whose cell areas are overlapped suchthat same frequency information is not included in the availablefrequency lists for the plurality of base stations.

The list creation unit may create the available frequency list for eachof the plurality of base stations by using wireless setup information ofeach of the plurality of base stations received from each of theplurality of base stations.

The list creation unit may recreate, in a case creation or recreation ofthe available frequency list is requested by a base station belonging toa group formed from two or more base stations, the available frequencylist of each base station belonging to the group.

The list creation unit may create the available frequency list based onthe number of communication terminals belonging to the base station.

The list creation unit may include, in the available frequency list forthe base station, a frequency band that is wider as the number ofcommunication terminals belonging to the base station is larger.

According to another embodiment of the present invention, there isprovided a base station which includes a wireless communication unit forwirelessly communicating with a communication terminal, a locationinformation acquisition unit for acquiring location information, alocation information transmission unit for transmitting the locationinformation acquired by the location information acquisition unit to amanagement server that creates an available frequency list by extractinga frequency corresponding to the location information, and a frequencysetting unit for setting a carrier frequency of the wirelesscommunication unit according to the available frequency list receivedfrom the management server.

According to another embodiment of the present invention, there isprovided a communication system which includes a base station includinga wireless communication unit for wirelessly communicating with acommunication terminal, a frequency setting unit for setting a carrierfrequency of the wireless communication unit, a location informationacquisition unit for acquiring location information, and a locationinformation transmission unit for transmitting the location informationacquired by the location information acquisition unit, and a managementserver including a holding unit for holding a location/frequency list inwhich location information and frequency information are associated, acreation unit for creating an available frequency list by extracting,from the location/frequency list, frequency information corresponding tothe location information received from the base station, and a listtransmission unit for transmitting the available frequency list createdby the creation unit to the base station. The frequency setting unitsets the carrier frequency of the wireless communication unit accordingto the available frequency list received from the management server.

According to another embodiment of the present invention, there isprovided a communication method including the steps of acquiring, by abase station, location information, transmitting, by the base station,the acquired location information to a management server holding alocation/frequency list in which location information and frequencyinformation are associated, creating, by the management server, anavailable frequency list by extracting, from the location/frequencylist, frequency information corresponding to the location informationreceived from the base station, transmitting, by the management server,the available frequency list to the base station, and setting, by thebase station, a carrier frequency according to the available frequencylist received from the management server.

According to the embodiments of the present invention described above,it is possible to prevent a case where communication by a base stationbecomes a cause of interference, by appropriately assigning a frequencyaccording to the location of the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing an overall configuration of acommunication system according to an embodiment of the presentinvention;

FIG. 2 is an explanatory diagram showing a configuration of a femtocellbase station according to a comparison example;

FIG. 3 is a function block diagram showing configurations of amanagement server and a femtocell base station 30 according to a firstembodiment of the present invention;

FIG. 4 is an explanatory diagram showing a configuration of a wirelesscommunication unit;

FIG. 5 is an explanatory diagram showing a concrete example of an unusedfrequency list;

FIG. 6 is an explanatory diagram schematically showing a creationprocess of an available frequency list creation unit for an availablefrequency list;

FIG. 7 is an explanatory diagram showing a relationship between aninstallation location of a femtocell base station and an availablefrequency;

FIG. 8 is an explanatory diagram showing a relationship between aninstallation location of a femtocell base station and an availablefrequency;

FIG. 9 is an explanatory diagram showing a relationship between aninstallation location of a femtocell base station and an availablefrequency;

FIG. 10 is a sequence chart showing an operation of a communicationsystem according to the first embodiment; and

FIG. 11 is a function block diagram showing configurations of amanagement server and a femtocell base station according to a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

Also, in this specification and the drawings, a plurality of structuralelements having substantially the same functional configuration may bedistinguished from each other by each having a different letter added tothe same reference numeral. For example, a plurality of elements havingsubstantially the same functional configuration are distinguished fromeach other as necessary as femtocell base stations 30A and 30B. However,if it is not particularly necessary to distinguish each of a pluralityof structural elements having substantially the same functionalconfiguration, only the same reference numeral is assigned. For example,if it is not particularly necessary to distinguish between the femtocellbase stations 30A and 30B, they are simply referred to as the femtocellbase stations 30.

Additionally, “DETAILED DESCRIPTION OF THE EMBODIMENT” will be describedin the item order below.

-   1. Overall Configuration of Communication System-   2. First Embodiment

2-1. Configurations of Management Server and Femtocell Base Stationaccording to First Embodiment

2-2. Operation of Communication System according to First Embodiment

-   3. Second Embodiment-   4. Summary

1. Overall Configuration of Communication System

First, an overall configuration of a communication system 1 according tothe first and second embodiments of the present invention will bedescribed with reference to FIG. 1.

FIG. 1 is an explanatory diagram showing the overall configuration ofthe communication system 1 according to the embodiment of the presentinvention. As shown in FIG. 1, the communication system 1 according tothe embodiment of the present invention includes a management server 10,the Internet 12, femtocell base stations 30A and 30B, and communicationterminals 20A to 20C.

The femtocell base station 30 is a small indoor base station compatiblewith a UMTS mobile phone wireless method standardized by 3GPP, forexample, and can connect with the communication terminal 20 having amobile phone interface compatible with the UMTS method. For example, inthe example shown in FIG. 1, the femtocell base station 30A is connectedwith the communication terminals 20A and 20B, and the femtocell basestation 30B is connected with the communication terminal 20C. Also,these femtocell base stations 30 are connected with the managementserver 10 via a broadband (BB) modem or a BB line and the Internet 12 orthe like.

Additionally, the femtocell base station 30 is only an example of a basestation controlling communication with the communication terminal 20,and the base station is not limited to the femtocell base station 30.For example, the embodiment of the present invention can also be appliedto a base station such as a microcell base station, a picocell basestation, and a relay station that relays communication between amacrocell base station and the communication terminal 20. Also, anexample is shown in FIG. 1 where only the two femtocell base stations30A and 30B are connected to the management server 10, but in reality, alarge number of femtocell base stations 30 are assumed to connect to themanagement server 10.

The communication terminal 20 can perform data communication withanother communication device via the femtocell base station 30. Forexample, the communication terminal 20 is capable of voice communicationor exchange of content data such as video data and voice data via thefemtocell base station 30.

Additionally, in FIG. 1, a mobile phone is shown as an example of thecommunication terminal 20, but the hardware of the communicationterminal 20 is not limited to a mobile phone. For example, thecommunication terminal 20 may also be an information processingapparatus, such as a personal computer (PC), a home video processingapparatus (such as a DVD recorder or a video cassette recorder), apersonal digital assistant (PDA), a home game machine, or a homeappliance. Furthermore, the communication terminal 20 may also be aninformation processing apparatus such as a personal handyphone system(PHS), a portable music playback device, a portable video processingdevice, a portable game machine, or the like.

The management server 10 is installed in a communications company'snetwork (core network of a communications company), for example, andperforms authentication of the femtocell base station 30, thecommunication terminal 20, and the like. Also, the management server 10holds an unused frequency list (location/frequency list) showing, foreach position, a frequency band not used by a macrocell base station,for example.

Here, a method performed by a femtocell base station to autonomouslydetect an unused frequency is also conceivable as a method performed bya femtocell base station to set an unused frequency at the installationlocation as a carrier frequency. In the following, the method performedby a femtocell base station to autonomously detect an unused frequencywill be specifically described with reference to FIG. 2.

FIG. 2 is an explanatory diagram showing a configuration of a femtocellbase station 90 according to a comparison example. As shown in FIG. 2,the femtocell base station 90 according to the comparison exampleincludes a monitored-frequency information holding unit 92, a receptionlevel detection unit 94, a frequency-to-be-used determination unit 96,and a frequency setting unit 98.

Information on a frequency to be monitored is held in themonitored-frequency information holding unit 92, and the reception leveldetection unit 94 detects a reception level of a frequency indicated bythe information held in the monitored-frequency information holding unit92.

The interference to a public macrocell due to usage of a frequency whosereception level detected by the reception level detection unit 94 isbelow a threshold is considered to be limited. Accordingly, thefrequency-to-be-used determination unit 96 determines a frequency whosereception level detected by the reception level detection unit 94 isbelow the threshold as the frequency to be used. Then, the frequencysetting unit 98 sets the frequency to be used determined by thefrequency-to-be-used determination unit 96 as a carrier frequency.

However, according to the configuration of this femtocell base station90, there is an underlying issue that, if the reception level detectionunit 94 is broken down, for example, a frequency that causesinterference to a public macrocell is erroneously set as the carrierfrequency. Furthermore, according to this configuration, it is assumedthat the number of frequencies that can be used will be fewer for thefemtocell base station 90 whose operation is started later, due to theuse of frequencies by the femtocell base stations 90 whose operationshave been started earlier. That is, unfairness due to the order of thetimings of start of operation may arise.

Furthermore, it is assumed that there are many time slots in whichwireless services by the femtocell base station 90 are not used, andthus it is assumed that a mechanism of variably assigning frequencybands according to the demand for wireless services will also beimportant.

Accordingly, the first and second embodiments of the present inventionhave come to be made from the standpoint of the circumstances describedabove. According to the embodiments of the present invention, it ispossible to prevent a case where communication by the femtocell basestation 30 becomes a cause of interference, to improve unfairness due tothe order of the timings of start of operation, and to dynamicallychange a frequency band to be assigned. In the following, the first andsecond embodiments of the present invention will be described in detail.

2. First Embodiment 2-1. Configurations of Management Server andFemtocell Base Station according to First Embodiment

FIG. 3 is a function block diagram showing configurations of themanagement server 10 and the femtocell base station 30 according to thefirst embodiment of the present invention.

As shown in FIG. 3, the management server 10 includes an unusedfrequency list holding unit 110, a list comparison unit 130, a networkcommunication unit 140, and an available frequency list creation unit150. Also, the femtocell base station 30 includes a GPS (GlobalPositioning System) antenna 310, a GPS reception unit 320, a memory card330 for authentication, a network communication unit 340, a frequencysetting unit 350, and a wireless communication unit 360.

The GPS antenna 310 of the femtocell base station 30 receives anavigation message transmitted from a satellite orbiting the Earth. TheGPS reception unit 320 acquires location information of the femtocellbase station 30 based on the navigation messages received by the GPSantenna 310 from a plurality of satellites.

As described, the GPS antenna 310 and the GPS reception unit 320function as location information acquisition units for acquiring thelocation information of the femtocell base station 30. However, the GPSantenna 310 and the GPS reception unit 320 are only configurationexamples for realizing the function of the location informationacquisition unit, and the function of the location informationacquisition unit may be realized by other configurations. For example, aconfiguration is also applicable of acquiring the current locationinformation based on the reception timing or the receiving power of awireless signal transmitted from a macrocell base station, a wirelessLAN base station (access point) or the like.

Authentication information is stored in the memory card 330 forauthentication, and authentication of the management server 10 and thefemtocell base station 30 is performed based on this authenticationinformation. According to such configuration, connection and operationof an illegal femtocell base station 30 can be prevented. Additionally,the memory card 330 for authentication may be a universal subscriberidentity module (USIM) mounted by a subscriber of the femtocell basestation 30, for example.

The network communication unit 340 exchanges various types ofinformation with the management server 10 via the Internet 12. Forexample, the network communication unit 340 functions as a locationinformation transmission unit for transmitting the location informationof the femtocell base station 30 intermittently acquired by the GPSreception unit 320. Also, the network communication unit 340 receives anavailable frequency list from the management server 10, transmitswireless setup information of the wireless communication unit 360 to themanagement server 10, or returns, regularly or in response to aninstruction from the management server 10, the available frequency listreceived from the management server 10.

The frequency setting unit 350 sets a carrier frequency of the wirelesscommunication unit 360 based on the available frequency list receivedfrom the management server 10 by the network communication unit 340.Specifically, frequency bands that the femtocell base station 30 isallowed to use are described in the available frequency list, and thefrequency setting unit 350 sets any of the frequency bands described inthe available frequency list as the carrier frequency of the wirelesscommunication unit 360.

The wireless communication unit 360 is an interface to the communicationterminal 20. The wireless communication unit 360 performs transmissionof wireless signals to the communication terminal 20 and reception ofwireless signals from the communication terminal 20 by using the carrierfrequency set by the frequency setting unit 350. In the following, adetailed configuration of the wireless communication unit 360 will bedescribed with reference to FIG. 4.

FIG. 4 is an explanatory diagram showing a configuration of the wirelesscommunication unit 360. As shown in FIG. 4, the wireless communicationunit 360 includes a wireless antenna 362, an antenna sharing unit 364, areception processing unit 366, and a transmission processing unit 368.

At the time of reception, the wireless antenna 362 and the receptionprocessing unit 366 are connected by the antenna sharing unit 364. Then,the wireless antenna 362 converts a wireless signal which has beenreceived to an electrical received signal, and supplies the same to thereception processing unit 366. The reception processing unit 366performs a receiving process (for example, down-conversion) so as toacquire information on the frequency band of the carrier frequency setby the frequency setting unit 350.

At the time of transmission, the wireless antenna 362 and thetransmission processing unit 368 are connected by the antenna sharingunit 364. Then, the transmission processing unit 368 processes (forexample, up-converts) a transmission signal so that a wireless signal istransmitted in the frequency band of the carrier frequency set by thefrequency setting unit 350, and the wireless antenna 362 transmits thewireless signal based on the transmission signal supplied from thetransmission processing unit 368.

Additionally, the frequency setting unit 350 may set all the frequencybands described in the available frequency list as the carrierfrequencies, or may set some of the frequency bands described in theavailable frequency list as the carrier frequencies. Furthermore, thefrequency setting unit 350 can variably set not only the carrierfrequency but also wireless parameters such as a modulation method,transmission power and a scramble code.

The network communication unit 140 of the management server 10 exchangesvarious types of information with the femtocell base station 30 via theInternet 12. For example, the network communication unit 140 functionsas a list transmission unit for transmitting an available frequency listcreated by the available frequency list creation unit 150. Also, thenetwork communication unit 140 intermittently receives the locationinformation of the femtocell base station 30 from the femtocell basestation 30, receives wireless setup information from the femtocell basestation 30, or receives an available frequency list returned from thefemtocell base station 30.

The unused frequency list holding unit 110 holds an unused frequencylist (location/frequency list) compiled from information on locallyunused frequencies. As shown in FIG. 5, a position (locationinformation) and an unused frequency band are associated in this unusedfrequency list. In the example shown in FIG. 5, frequency bands f1, f2,and f3 are the unused frequency bands at position A.

Additionally, the expression method of each position is not particularlylimited. For example, each position may be expressed by a latitude rangeand a longitude range, such as “35.01 to 35.02 north latitudes, 135.01to 135.03 east longitudes,” or may be expressed by a centre position anda radius distance, such as “centre position: 35.01 north latitude,radius 500 m.”

The available frequency list creation unit 150 (list creation unit)creates the available frequency list for the femtocell base station 30based on the unused frequency list held in the unused frequency listholding unit 110 and the location information of the femtocell basestation 30 received from the femtocell base station 30 by the networkcommunication unit 140.

Specifically, the available frequency list creation unit 150 extractsunused frequencies corresponding to the location information of thefemtocell base station 30 from the unused frequency list, and createsthe available frequency list. For example, if the location informationof the femtocell base station 30 is within the range of position A, theavailable frequency list creation unit 150 extracts frequencies f1, f2,and f3 from the unused frequency list shown in FIG. 5, and creates anavailable frequency list including frequencies f1, f2, and f3.

Additionally, the femtocell base station 30 does not necessarily use allthe frequencies included in the available frequency list. For example,sometimes, the femtocell base station 30 uses only frequency f1 in theavailable frequency list including frequencies f1, f2, and f3. With sucha case in mind, the available frequency list creation unit 150 mayrecreate the available frequency list for the femtocell base station 30by perceiving the frequency being used by the femtocell base station 30based on the wireless setup information received from the femtocell basestation 30. For example, in a case the femtocell base station 30 isusing only frequency f1, the available frequency list creation unit 150may recreate the available frequency list including only frequency f1.According to such configuration, it is possible to assign otherfrequencies such as frequencies f2 and f3 to other femtocell basestations 30 as available frequencies.

As described, by providing the available frequency list creation unit150 in the management server 10, the available frequency list creationunit 150 is managed by an organization which is at least licensed toprovide public services or for which equal reliability is guaranteed,and thus the security of the system can be ensured.

Furthermore, the femtocell base station 30 intermittently transmits thelocation information to the management server 10. Accordingly, even ifthe installation location of the femtocell base station 30 isintentionally or accidentally moved, the available frequency listcreation unit 150 can create the available frequency list according tothe installation location after the move, and thus a case where afrequency band which can become the cause of interference is used by thefemtocell base station 30 can be prevented.

Additionally, there may also be assumed a case where the locationinformation is not received from the femtocell base station 30 due tobreakdown of the GPS reception unit 320 or the like. In such a case, theavailable frequency list creation unit 150 may, as fail-safe control,create the available frequency list based on an address included insubscriber information of the femtocell base station 30.

Furthermore, the list comparison unit 130 of the management server 10compares the available frequency list transmitted to the femtocell basestation 30 and the available frequency list returned from the femtocellbase station 30. According to this configuration, the availablefrequency list can be prevented from being rewritten withoutauthorization on the side of the femtocell base station 30, therebypreventing use of an illegal frequency band.

(Creation Method of Available Frequency List)

Here, the creation method of the available frequency list will bedescribed in greater detail. In the above, an example where the locationinformation received from the femtocell base station 30 is used forcreation has been described, but in the following, an example where thewireless setup information of the femtocell base station 30 is also usedin addition to the location information will be described.

FIG. 6 is an explanatory diagram schematically showing a creationprocess of the available frequency list creation unit 150 for theavailable frequency list. As shown in FIG. 6, the available frequencylist creation unit 150 creates the available frequency list for eachfemtocell base station 30 based on the location information and thewireless setup information received from each femtocell base station 30and the unused frequency list held in the unused frequency list holdingunit 110. Additionally, as the wireless setup information, variouswireless parameters such as a frequency band used as a carrier, amodulation method, and transmission power can be cited.

For example, a case is considered as shown in FIG. 7 where it isdecided, based on information received from each femtocell base station30, that there is no other femtocell base station 30 near the femtocellbase station 30A installed within the range of position A. In this case,the available frequency list creation unit 150 can assign all offrequencies f1, f2, and f3 that are not used at position A to thefemtocell base station 30A as available frequencies.

Also, a case is considered as shown in FIG. 8 where it is decided, basedon information received from each femtocell base station 30, that thefemtocell base stations 30A and 30B are present within the range ofposition A. Here, the square of radius rx of the cell area of thefemtocell base station 30A is proportional to the transmission power ofthe femtocell base station 30A, and the square of radius ry of the cellarea of the femtocell base station 30B is proportional to thetransmission power of the femtocell base station 30B. Therefore, radiirx and ry of the cell areas of the femtocell base stations 30A and 30Bcan be each calculated based on the transmission power included in thewireless setup information.

When it is decided by the calculation above that, as shown in FIG. 8,the cell areas of the femtocell base stations 30A and 30B do notoverlap, it is assumed that no interference is caused even if thefemtocell base stations 30A and 30B use the same frequency. Accordingly,the available frequency list creation unit 150 can assign all offrequencies f1, f2, and f3 that are not used at position A to both ofthe femtocell base stations 30A and 30B as the available frequencies.

A case is considered where operation of the femtocell base station 30Cis then started at a position where its cell area overlaps with the cellareas of the femtocell base stations 30A and 30B, as shown in FIG. 9.The available frequency list creation unit 150 creates, for interferenceprevention, the available frequency list for each of the femtocell basestations 30 in such a way that the same frequency is not included in theavailable frequency lists of femtocell base stations 30 whose cell areasoverlap. Therefore, in a case operation of the femtocell base station30C is started as described above, if unused frequencies f1, f2, and f3are all already assigned to the femtocell base stations 30A and 30B, itis not possible to assign an available frequency to the femtocell basestation 30C.

Thus, in the present embodiment, a configuration is adopted where theavailable frequency lists for the femtocell base stations 30A and 30Bare recreated at the time of start of operation of the femtocell basestation 30C so that no unfairness arises due to the order of the timingsof start of operation.

For example, in the case operation of the femtocell base station 30C isto be started, the available frequency list creation unit 150 recreatesthe available frequency list including frequency f1 for the femtocellbase station 30A, recreates the available frequency list includingfrequency f3 for the femtocell base station 30B, and recreates theavailable frequency list including frequency f2 for the femtocell basestation 30C, as shown in FIG. 9.

As has been described above, by recreating, in the case operation of anew femtocell base station is to be started, the available frequencylists for other femtocell base stations whose cell areas overlap withthat of the new femtocell base station, frequency resources can befairly and effectively used by respective femtocell base stationswithout being affected by the order of the timings of start of operationof respective femtocell base stations.

Additionally, in the above, an example has been described where theavailable frequency list is recreated for an existing femtocell basestation whose cell area overlaps with that of the new femtocell basestation, but the present invention is not limited to such an example.For example, the management server 10 may group a plurality of femtocellbase stations 30 based on addresses included in pieces of subscriberinformation of the femtocell base stations 30 or of a BB line, and mayrecreate the available frequency list on a per-group basis.

Furthermore, the timing of recreating the available frequency list isnot limited to the timing of start of operation of a new femtocell basestation. For example, the available frequency list creation unit 150 mayrecreate the available frequency lists for a plurality of femtocell basestations 30 with the overlapping cell areas or that are in the samegroup, in response to a request from an existing femtocell base station30.

2-2. Operation of Communication System according to First Embodiment

In the foregoing, the configurations of the femtocell base station 30and the management server 10 according to the first embodiment have beendescribed. Next, an operation of the communication system 1 according tothe first embodiment will be described with reference to FIG. 10.

FIG. 10 is a sequence chart showing an operation of the communicationsystem 1 according to the first embodiment. As shown in FIG. 10, first,the GPS reception unit 320 of the femtocell base station 30 acquires thelocation information of the femtocell base station 30 (S210). Then, thenetwork communication unit 340 of the femtocell base station 30transmits the location information acquired by the GPS reception unit320 to the management server 10 (S220).

Next, the available frequency list creation unit 150 of the managementserver 10 creates the available frequency list based on the unusedfrequency list held by the unused frequency list holding unit 110 andthe location information received from the femtocell base station 30(S230). Specifically, the available frequency list creation unit 150creates the available frequency list by extracting unused frequencycorresponding to the location information of the femtocell base station30 from the unused frequency list.

Furthermore, the network communication unit 140 of the management server10 transmits the available frequency list created by the availablefrequency list creation unit 150 to the femtocell base station 30(S240).

Then, when the available frequency list is received from the managementserver 10, the frequency setting unit 350 of the femtocell base station30 sets all or some of the frequencies included in the availablefrequency list as the carrier frequency of the wireless communicationunit 360 (S250). Next, the network communication unit 340 of thefemtocell base station 30 transmits the wireless setup information ofthe wireless communication unit 360 to the management server 10, andreturns the available frequency list received from the management server10 to the management server 10 (S260).

Then, the list comparison unit 130 of the management server 10 comparesthe available frequency list transmitted to the femtocell base station30 and the available frequency list returned from the femtocell basestation 30 (S270). This can prevent the available frequency list frombeing rewritten without authorization on the side of the femtocell basestation 30, thereby preventing use of an illegal frequency band.

Furthermore, with the processes of S210 to S270 being repeated by themanagement server 10 and the femtocell base station 30, even if theinstallation location of the femtocell base station 30 is moved, theavailable frequency list according to the installation location afterthe move can be created. As a result, use of a frequency band which canbe a cause of interference by the femtocell base station 30 can beprevented.

3. Second Embodiment

In the foregoing, the first embodiment of the present invention has beendescribed. Next, the second embodiment of the present invention will bedescribed with reference to FIG. 11.

FIG. 11 is a function block diagram showing configurations of amanagement server 10′ and a femtocell base station 30′ according to thesecond embodiment of the present invention. As shown in FIG. 11, themanagement server 10′ includes an unused frequency list holding unit110, a list comparison unit 130, a network communication unit 140, andan available frequency list creation unit 152. Also, the femtocell basestation 30′ includes a GPS antenna 310, a GPS reception unit 320, amemory card 330 for authentication, a network communication unit 340, afrequency setting unit 350, a wireless communication unit 360, and aterminal number management unit 370.

Additionally, the management server 10′ and the femtocell base station30′ according to the second embodiment of the present invention sharethe common configurations with the management server 10 and thefemtocell base station 30 according to the first embodiment, and thusexplanation will be mainly given on the difference between the first andsecond embodiments.

The terminal number management unit 370 of the femtocell base station30′ manages the number of communication terminals 20 belonging to thefemtocell base station 30′. Specifically, the terminal number managementunit 370 manages the number of communication terminals 20 present withinthe cell area of the femtocell base station 30′ or the number ofcommunication terminals 20 currently connected to the femtocell basestation 30′.

The network communication unit 340 of the femtocell base station 30′transmits the number of terminals managed by the terminal numbermanagement unit 370 to the management server 10′ via the Internet 12,and the network communication unit 140 of the management server 10′receives the number of terminals.

The available frequency list creation unit 152 of the management server10′ creates an available frequency list for the femtocell base station30′ based on, in addition to location information and wireless setupinformation of the femtocell base station 30′, the number of terminalsreceived by the network communication unit 140.

Specifically, in the case the number of communication terminals 20belonging to the femtocell base station 30′ is small, the availablefrequency list creation unit 152 assigns a narrow frequency band to thefemtocell base station 30′ as the available frequency. On the otherhand, in the case the number of communication terminals 20 belonging tothe femtocell base station 30′ is large, the available frequency listcreation unit 152 assigns a wide frequency band to the femtocell basestation 30′ as the available frequency. Also, the terminal numbermanagement unit 370 may also have a function of performing weighting,taking into account information on Quality of Service (QoS) desired byeach terminal. For example, in the case a terminal starts an applicationfor which high QoS is wanted, the terminal is notified to the managementserver 10′ to be more than one terminal, thereby enabling assignment ofa wide frequency band to the femtocell base station 30′ as the availablefrequency.

According to such a configuration, frequency resources can bedynamically assigned to each femtocell base station 30′ according tocommunication demand, and thus an appropriate amount of frequencyresources can be distributed to each femtocell base station 30′.

4. Summary

As has been described above, in the embodiment of the present invention,by providing the available frequency list creation unit 150 (152) to themanagement server 10 (10′), the available frequency list creation unit150 (152) is managed by an organization which is at least licensed toprovide public services or which is trusted with equal reliability, andthus the security of the system can be ensured.

Furthermore, the femtocell base station 30 (30′) intermittentlytransmits location information to the management server 10 (10′).Accordingly, even if the installation location of the femtocell basestation 30 (30′) is intentionally or accidentally moved, the availablefrequency list creation unit 150 (152) can create an available frequencylist according to the installation location after the move, and thus acase where a frequency band which can become the cause of interferenceis used by the femtocell base station 30 (30′) can be prevented.

Furthermore, the list comparison unit 130 of the management server 10(10′) compares the available frequency list transmitted to the femtocellbase station 30 (30′) and the available frequency list returned,periodically or in response to an instruction from the management server10 (10′), from the femtocell base station 30 (30′). According to thisconfiguration, the available frequency list can be prevented from beingrewritten without authorization on the side of the femtocell basestation 30 (30′), thereby preventing use of an illegal frequency band.

Furthermore, by recreating, in the case operation of a new femtocellbase station is to be started, the available frequency lists for otherfemtocell base stations whose cell areas overlap with that of the newfemtocell base station, frequency resources can be fairly andeffectively used by respective femtocell base stations without beingaffected by the order of the timings of start of operation of respectivefemtocell base stations.

Furthermore, according to the second embodiment of the presentinvention, frequency resources can be dynamically assigned to eachfemtocell base station 30′ according to communication demand, and thusan appropriate amount of frequency resources can be distributed to eachfemtocell base station 30′.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

For example, the steps of the processing of the communication system 1according to the present specification do not necessarily have to beprocessed chronologically according to the order described as thesequence chart. For example, the steps of the processing of thecommunication system 1 can also be processed in an order different fromthat described as the sequence chart or may be processed in parallel.

Furthermore, a computer program for causing hardware, such as a CPU, aROM, or a RAM, embedded in the femtocell base station 30 or in themanagement server 10 to realize an equivalent function as each elementof the femtocell base station 30 or of the management server 10described above can also be created. Furthermore, a storage mediumstoring the computer program is also provided.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2010-070266 filedin the Japan Patent Office on Mar. 25, 2010, the entire content of whichis hereby incorporated by reference.

What is claimed is:
 1. A management server comprising: at least oneprocessor configured to: hold a location/frequency list in whichlocation information 32and frequency information are associated; createa first available frequency list by extracting, from thelocation/frequency list, frequency information based on: locationinformation received from a base station and wireless setup informationof the base station received from the base station, wherein the wirelesssetup information comprises a modulation method, a transmission power,and/or a frequency band used as a carrier; and transmit the firstavailable frequency list to the base station.